Optical alignment method for binocular displays

ABSTRACT

An optical alignment device for binocular displays is provided which comprises a pair of objective lenses and adjacent lens apertures for receiving the images transmitted along the two optical axes of the binocular display and optical folding means in the form of folding mirrors, right-angle prisms, or the like, disposed along each said optical axis for optically folding said images along a single optical axis, whereby the said images may be focused as a single composite image on an imaging plane.

This is a continuation of application Ser. No. 441,815, filed Nov. 11,1982.

RIGHTS OF THE GOVERNMENT

The invention described herein may be manufactured and used by or forthe Government of the United States for all governmental purposeswithout the payment of any royalty.

BACKGROUND OF THE INVENTION

This invention relates generally to the field of optical alignmentsystems and more particularly to a novel optical device for detectingmisalignment in a binocular display by superimposition of the twobinocular display images.

The present invention provides a simple and easy-to-use device fordetermining the disparity between the images transmitted along theoptical axes of a binocular display system. The invention findsparticular utility for the alignment, adjustment or calibration ofbinocular helmet mounted displays and other optical devices employingwide field of view binocular displays.

The invention comprises a pair of objective lenses for receiving theimages transmitted along the two optical axes of the binocular displayand focusing the images on an imaging plane for viewing. The imagestransmitted by the objective lenses are folded onto a single opticalaxis, using folding mirrors, right angle prisms, or the like, insertedalong each optical axis of the binocular system, and displayed on areticle mounted in the imaging plane as a single superimposed image.Means may be included to provide equal optical path lengths along eachbinocular optical axis from the lenses to the reticle. For a properlyaligned binocular display system, the two images transmitted along thetwo binocular optical axes and superimposed using the optics of thepresent invention will appear as a single, well-defined image on theimaging plane. Disparity in alignment of the binocular display betweenthe two optical axes is detected by the device of the present inventionas a diffuse or double image.

It is therefore an object of the present invention to provide animproved optical alignment device.

It is a further object of the present invention to provide a device fordetecting misalignment of a binocular optical display system.

It is yet another object of the present invention to provide a devicefor checking the alignment of helmet mounted binocular displays.

These and other objects of the present invention will become apparent asthe detailed description of certain representative embodiments thereofproceeds.

SUMMARY OF THE INVENTION

In accordance with the foregoing principles and objects of the presentinvention, an optical alignment device for binocular displays isprovided, which comprises a pair of objective lenses and adjacent lensapertures for receiving the images transmitted along the two opticalaxes of the binocular display and optical folding means in the form offolding mirrors, right angle prisms, or the like, disposed along eachsaid optical axis for optically folding said images along a singleoptical axis, whereby the said images may be focused as a singlecomposite image on an imaging plane.

DESCRIPTION OF THE DRAWING

The present invention will be more clearly understood from the followingdetailed description of certain representative embodiments thereof readin conjunction with the accompanying drawing FIGURE which is a schematicplan view of a representative arrangement of optical components whichthe invention comprises.

DETAILED DESCRIPTION

Referring now to the accompanying drawing, shown therein is a schematicplan view of a novel binocular alignment/measurement device of thepresent invention. As shown therein, a pair of objective lens apertures11a and 11b and objective lenses 12a and 12b are configured to besupported near the exit pupils 3a and 3b of the binocular opticaldisplay device 2 requring adjustment, alignment or calibration, andalong the optical axes A and B of device 2 substantially as shown. Theapertures 11a and 11b are selected to have openings of about thediameter of the pupil of the eye (about 2 mm to about 8 mm) in order toclosely approximate in the alignment device the image conception of anobservor O using the binocular optical display device 2 underoperational conditions. Apertures 11a and 11b, lenses 12a and 12b, alongwith the remaining optical components hereinafter described which theinvention herein includes may be supported in conventional fashionwithin a housing or other support structure 13.

Objective lenses 12a and 12b and apertures 11a and 11b are aligned toreceive the images 4a and 4b of an object under observation astransmitted through display device 2 and represented by light rays 5aand 5b. The focal lengths of each lens 12a and 12b are selected in orderto focus the images 4a and 4b on an imaging plane I, on which acalibrated reticle 14 may be mounted, at the focal plane of eyepiece 15as seen by observer O.

Optical folding means in the form of a pair of folding mirrors or a pairof right-angle prisms 16 and 17 are provided in order to fold image 4a,as transmitted by lens 12a, along a single optical axis C and throughbeamsplitter 18 onto the imaging plane of reticle 14 for viewing througheyepiece 15. Image 4b, as transmitted by lens 12b is folded onto opticalaxis C using folding means in the form of a folding mirror orright-angle prism 19 and the reflective plane of beamsplitter 18substantially as showing in the drawing. A glass compensating block 20of appropriate thickness may be inserted between lens 12b and prism 19to ensure identical optical path lengths for light rays 5a and 5b.

The images 4a and 4b are therefore combined by beamsplitter 18 to form asingle image 4a, 4b on the imaging plane of reticle 14 as observed byobserver O.

If optical display device 2 is in proper optical alignment, then images4a and 4b will superimpose on each other at reticle 14 and appear toobserver O as a single, well-defined image 4a, 4b. Misalignment ofdisplay device 2 may be easily detected since the image produced atreticle 14 would appear as a double or diffuse image consistent with thedegree of misalignment. Alignment of display device 2 using thealignment device of this invention may then be perfected by suitablyadjusting display device 2 until a distinct, single image 4a, 4b isobserved on reticle 14.

The supporting structure 13 may desirably include means, shownschematically in the accompanying drawing as adjustable connector 21interconnecting apertures 11a, b, lenses 12a, b, and prisms 16 and 19,to adjust the spacing between lenses 12a, b and apertures 11a, b toaccommodate a wide range of exit pupils 3a, 3b spacings of variousbinocular display devices 2.

It is instructive to note that the system of the present invention couldbe configured so that the entire optical system can be inverted, suchthat an alignment determination for display device 2 first made withlenses 12a and 12b near, respectively, exit pupils 3a and 3b, may bechecked by inverting the alignment device so that aperture 11a confrontsexit pupil 3b and aperture 11b confronts exit pupil 3a, and thenrechecking the alignment of display device 2.

The optical alignment device of the present invention may also be usedto assess the divergence or convergence of a single exit pupil displaydesigned to be observed by both eyes of an observer simultaneously, suchas a head-up display. For this application, a determination of thedegree of disparity is made from the image on the reticle comprising thetwo images of the display as transmitted through the device.

The present invention, as hereinabove described, therefore provides anovel optical device for detecting misalignment in binocular displays.It is understood that certain modifications to the invention asdescribed may be made, as might occur to one with skill in theapplicable field, within the intended scope of the appended claims.Therefore, all optical component arrangements contemplated hereunderwhich achieve the objects of the present invention have not been shownin complete detail. Other embodiments may be developed without departingfrom the spirit of this invention or from the scope of the appendedclaims.

I claim:
 1. A method for detecting misalignment in a binocular displaysystem having first and second optical axes, which comprises the stepsof:a. forming identical first and second images transmitted,respectively, along said first and second optical axes from saidbinocular display system; b. forming a composite image of said first andsecond images by projecting said first and second images alongrespective optical paths of identical optical lengths and opticallyfolding said first image onto said second image and projecting saidcomposite image along a third optical axis; c. providing means definingan imaging plane along said third optical axis for displaying saidcomposite image; d. displaying said composite image on said imagingplane; and e. comparing said first and second images in said compositeimage as displayed on said imaging plane defining means to detectmisalignment of said first and second images.
 2. The method as recitedin claim 1 wherein the step of forming said composite image is performedby folding said first and second images along said third optical axisutilizing first and second folding mirrored surfaces disposed,respectively, along said first and second optical axes, a third foldingmirrored surface disposed along said third optical axis and in opticalalignment with said first mirrored surface, and a beamsplitter disposedalong said third optical axis and in optical alignment with said secondand third mirrored surfaces.
 3. The method as recited in claim 2 whereinsaid mirrored surfaces utilized in said step of forming said compositeimage comprise the reflective surfaces of right-angle prisms and whereinan optical path length compensating block is disposed along said secondoptical axis.
 4. The method as recited in claim 2 including first andsecond objective lenses disposed, respectively, along said first andsecond optical axes, and first and second aperture defining meansadjacent respective said first and second objective lenses and betweensaid objective lenses and said binocular display system, for formingsaid first and second images.
 5. The method as recited in claim 4including adjusting means, interconnecting said aperture defining means,objective lenses and folding mirrored surfaces, for selectively aligningsaid objective lenses along respective said first and second opticalaxes.
 6. The method as recited in claim 1 wherein said imaging planedefining means comprises a reticle for displaying said composite image,and wherein an eyepiece is included for viewing said composite imagedisplayed on said reticle.